We plan to continue to quantify multiple components of functional performance in patients with selected neuro-musculo-skeletal disabilities. With these data, we will study and identify basic mechanisms which cause abnormal kinetics and kinematics in individual patients spasticity and rigidity, joint immobility, postural unsteadiness and upright instability. The abnormal gait patterns and other components of function will be compared with standards of normal variability which we have established for appropriate age and sex groups (for example, standards for walking performance and standards for muscle strength). We will continue to establish such standards as we expand our ability to quantify other aspects of function, such as resistance to passive rotation, phases of muscle activity and ground reactions during gait. In addition to gaining further insight into the nature of certain gait disorders, we plan to document the characteristic features of the gait abnormalities of selected disease states and document the changes in functional performance after various medical or surgical treatments or the changes due to use of assistive devices such as canes, crutches, prostheses or orthoses.